1985 Ferrari 400i Green Sensor harness question

So, I am putting a 400i back together. Engine was rebuilt. Mechanic lost half the plumbing parts and died.... I am connecting the "green" sensor harness back up. It runs from the back of the engine along the middle of the engine and another branch goes to the front over the the drivers side and back along the passenger side bank towards the passenger seat. Amongst many other sensors, it connects to the the oil pressure switch at the front center top of the engine.

It is all good EXCEPT, I have a SPARE spade connector with a green boot at the back center top of the engine. It looks identical to the spade/boot that connects to the above oil pressure switch. What the heck does it connect to, please? I have been all over the top back of the engine and I am not seeing it. I have also poured over the official documentation and it is eluding me.

 

thanks in advance for your inputs